Impact Of Critical Path Method (CPM) Of Scheduling On On-Time Completion Of Transportation Projects

This study addresses the effectiveness of Critical Path Method (CPM) scheduling on project delivery. Specifically, the on-time completion of projects with and without a CPM schedule is explored. The paper uses data from 2,097 South Carolina transportation projects let after February 2008 and substantially completed by August 2015. The delay analysis uses the original contract completion date as well as the completion date adjusted by change orders. Chi-Squared tests are used to examine the relationship between CPM scheduled projects and delayed projects, and t-tests are used to compare the mean delay (in days) between CPM scheduled and unscheduled projects. The results of these tests indicate that both the fraction of delayed projects and the mean delay (in days) are larger in projects with CPM schedules. Several conjectures that explain these unexpected results are given. A nationwide survey was conducted to find out the viewpoint on CPM schedules of state Departments of Transportation(DOTs), resident construction engineers and contractors. The survey revealed that most state DOTs use CPM along with Gantt chart for scheduling and perceived complexity and risk are used to select projects for CPM schedules. Resident construction engineers indicated that delay before the start of work on the field do not impact the overall duration of the project. The contractors acknowledge the importance of CPM schedules but they sometimes fail to make most out of CPM schedules. The issues regarding selection criteria, enforcing and skilled person for CPM schedules are addressed in the study and recommendations are provided